It is a mode of training where the body weight (or a fraction thereof) is used to provide the resistance in a great variety of exercises. The equipment used is a Total Gym (or its successor, the Power Tower which I call Total Gym on steroids.)
I have owned the Total Gym and now have the Power Tower. It is my favorite piece of ‘equipment’. It is extremely versatile and can even double up for many Pilates Reformer exercises. As it always operates on a percent of body weight, it is a great equalizer but starts at a very low level of resistance and is therefore usable for the very de-conditioned.
And as a last note: I derive no benefits from this endorsement. efi did not even know it was coming.